| 1. |
- Kelkensberg, F., et al.
(author)
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Molecular Dissociative Ionization and Wave-Packet Dynamics Studied Using Two-Color XUV and IR Pump-Probe Spectroscopy
- 2009
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In: Physical Review Letters. - 1079-7114. ; 103:12
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Journal article (peer-reviewed)abstract
- We present a combined theoretical and experimental study of ultrafast wave-packet dynamics in the dissociative ionization of H-2 molecules as a result of irradiation with an extreme-ultraviolet (XUV) pulse followed by an infrared (IR) pulse. In experiments where the duration of both the XUV and IR pulses are shorter than the vibrational period of H-2+, dephasing and rephasing of the vibrational wave packet that is formed in H-2+ upon ionization of the neutral molecule by the XUV pulse is observed. In experiments where the duration of the IR pulse exceeds the vibrational period of H-2+ (15 fs), a pronounced dependence of the H+ kinetic energy distribution on XUV-IR delay is observed that can be explained in terms of the adiabatic propagation of the H-2+ wave packet on field-dressed potential energy curves.
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| 2. |
- Ghafur, Ala A., et al.
(author)
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Tectonic Development of Northeastern part of the Arabian Plate: Examples from Pirmam and Bana Bawi Anticlines in the Kurdistan Region of North Iraq
- 2023
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In: Results in Geophysical Sciences. - : Elsevier. - 2666-8289. ; 14
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Journal article (peer-reviewed)abstract
- The Pirmam and Bana Bawi anticlines are two elongated anticlines located in the central northern part of the Kurdistan Region of north Iraq (KRI), in the northeastern part of the Arabian Plate. We have used satellite images and geological maps to interpret the presented data and to calculate the rates of uplift and down wards (subsidence) amounts, besides estimating the rates of deposition and incision of some alluvial fans and stream terraces. Most of the achieved data were checked in the field. In the Pirmam anticline the rate of the uplift and subsidence is 8.613 mm/ 100 year and 7.962 mm/ 100 year, respectively, whereas in the Bana Bawi anticline the rates are 3.036 mm/ 100 year and 4.365 mm/100 year, respectively. The indications of the lateral growth are the presence of water gaps, wind gaps, en-echelon plunging, whale-back shape and different types of valleys. We have calculated the depositional and incision rates in the Kori and Bastoora streams. They are 5.204 mm/ 100 year and 5.555 mm/ 100 year, respectively in the former, whereas in the latter are 3.469 mm/100 year and 8.731 mm/ 100 year, respectively. Moreover, we have calculated the depositional and incision rates in old and recent alluvial fans. In the former, they are 1.665 mm/ 100 year and 0.722 mm/ 100 year, respectively, whereas in the latter are 3.036 and 4.365 mm/ 100 years, respectively.
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| 3. |
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| 4. |
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| 5. |
- Lepine, F., et al.
(author)
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Short XUV pulses to characterize field-free molecular alignment
- 2007
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In: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 54:7, s. 953-966
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Journal article (peer-reviewed)abstract
- We present experiments on field-free molecular alignment of N-2 and CO2 probed with short XUV pulses that are obtained via high-harmonic generation. The XUV pulses induce a dissociative ionization or a Coulomb explosion of the molecule, where the fragment ion recoil (measured using the velocity map imaging technique) provides information on the alignment of the parent molecule at the time of ionization. We discuss how photoelectron detection may in future allow the determination of molecular-frame photoelectron angular distributions and molecular structure.
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| 6. |
- Mauritsson, Johan, et al.
(author)
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Attosecond Electron Spectroscopy Using a Novel Interferometric Pump-Probe Technique
- 2010
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In: Physical Review Letters. - 1079-7114. ; 105:5
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Journal article (peer-reviewed)abstract
- We present an interferometric pump-probe technique for the characterization of attosecond electron wave packets (WPs) that uses a free WP as a reference to measure a bound WP. We demonstrate our method by exciting helium atoms using an attosecond pulse (AP) with a bandwidth centered near the ionization threshold, thus creating both a bound and a free WP simultaneously. After a variable delay, the bound WP is ionized by a few-cycle infrared laser precisely synchronized to the original AP. By measuring the delay-dependent photoelectron spectrum we obtain an interferogram that contains both quantum beats as well as multipath interference. Analysis of the interferogram allows us to determine the bound WP components with a spectral resolution much better than the inverse of the AP duration.
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| 7. |
- Miles, J., et al.
(author)
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A new technique for probing chirality via photoelectron circular dichroism
- 2017
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In: Analytica Chimica Acta. - Amsterdam : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 984, s. 134-139
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Journal article (peer-reviewed)abstract
- We present a proof-of-principle approach for discriminating chiral enantiomers based on the phenomenon of multiphoton photoelectron circular dichroism. A novel stereo detection setup was used to measure the number of photoelectrons emitted from chiral molecules in directions parallel or antiparallel to the propagation of the ionising femtosecond laser pulses. In this study, we show how these asymmetries in the ketones camphor and fenchone depend upon the ellipticity of the laser pulses and the enantiomeric excess of the sample. By using a high repetition rate femtosecond laser, enantiomer excesses with uncertainties at the few-percent level could be measured in close to real-time. As the instrument is compact, and commercial turnkey femtosecond lasers are readily available, the development of a stand-alone chiral analysis instrument for a range of applications is now possible.
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| 8. |
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| 9. |
- Sansone, G., et al.
(author)
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Attosecond excitation of electron wavepackets
- 2008
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In: Quantum Electronics and Laser Science Conference, QELS 2008. - 9781557528599
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Conference paper (peer-reviewed)abstract
- We present experiments, supported by time-dependent Schrödinger simulations, on the dynamics of Helium bound states after an attosecond excitation in the presence of a strong infrared laser field.
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| 10. |
- Sansone, G., et al.
(author)
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Electron localization following attosecond molecular photoionization
- 2010
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 465:7299, s. 3-763
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Journal article (peer-reviewed)abstract
- For the past several decades, we have been able to directly probe the motion of atoms that is associated with chemical transformations and which occurs on the femtosecond (10(-15)-s) timescale. However, studying the inner workings of atoms and molecules on the electronic timescale(1-4) has become possible only with the recent development of isolated attosecond (10(-18)-s) laser pulses(5). Such pulses have been used to investigate atomic photoexcitation and photoionization(6,7) and electron dynamics in solids(8), and in molecules could help explore the prompt charge redistribution and localization that accompany photoexcitation processes. In recent work, the dissociative ionization of H-2 and D-2 was monitored on femtosecond timescales(9) and controlled using few-cycle near-infrared laser pulses(10). Here we report a molecular attosecond pump-probe experiment based on that work: H-2 and D-2 are dissociatively ionized by a sequence comprising an isolated attosecond ultraviolet pulse and an intense few-cycle infrared pulse, and a localization of the electronic charge distribution within the molecule is measured that depends-with attosecond time resolution-on the delay between the pump and probe pulses. The localization occurs by means of two mechanisms, where the infrared laser influences the photoionization or the dissociation of the molecular ion. In the first case, charge localization arises from quantum mechanical interference involving autoionizing states and the laser-altered wavefunction of the departing electron. In the second case, charge localization arises owing to laser-driven population transfer between different electronic states of the molecular ion. These results establish attosecond pump-probe strategies as a powerful tool for investigating the complex molecular dynamics that result from the coupling between electronic and nuclear motions beyond the usual Born-Oppenheimer approximation.
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